Surrounded by tall buildings and the hustle and bustle of Causeway Bay, the role of Victoria Park in providing a haven for the public is vital, according to an urban forestry expert.

That's especially true given that the city has just three square metres of urban park space per resident, according to Professor Jim Chi-yung, of the University of Hong Kong. In Taiwan, the ratio is more than five square metres per person and in Singapore it is seven to eight per person. In European cities, each resident enjoys more than 10 times as much parkland as in Hong Kong.

"Urban parks mainly provide outdoor recreational venues, and in Hong Kong, an ultra compact city, that is especially important," Jim said. "Only a few, rich people in Hong Kong have their own private open space, some in the form of gardens. And clubhouses are reserved for their members as well."

Built in 1957, Victoria Park is the largest urban park on Hong Kong Island. Besides providing fresher air than the surrounding streets, the presence of the park also allows more sunlight to reach buildings in the area.

"If an area contains only skyscrapers, no sunlight can enter flats on the lower floors," Jim said. "If residents can see little sky and get little exposure to sunlight, the impact on their physical and mental health is huge. We're only aware of it subconsciously, but that's an in-born mechanism."

The park also keeps the city's air a little cooler, and provides a filter for rainwater before it flows into the sea, he says.

"The government is usually only concerned about the recreational purpose of parks. When it comes to their role in the ecosystem, they pay no attention."

The construction of a road through the park would mean poorer air quality and a noisier environment, he said.

"The park is already very noisy. When people go to a park, they look for tranquility."

The environmental assessment on the project found that about 2,400 square metres of the park will be "alienated" - cut off from the main body - by the road. The alienated land will be accessible from the rest of the park only at the point where the road passes underground, the Highways Department says.

Jim said the cut off portion of the park would still be physically there, but park users would be less interested in visiting it.

"Its existence would be nullified," he said.

Video: What the construction work in Victoria Park looks like

Jim is also concerned about the way trees are being transplanted from the affected area of the park. A visit by the Post earlier this month found branches of trees had been cut in preparation for the move. Only the trunk and a few bigger branches were left on each tree.

Jim says that method of relocation "belongs to the 19th century". He said international standards required root balls for each tree being transplanted to be at least 10 times the diameter of the trunk, but that some trees were being transplanted at a ratio of just five times.

The department said all tree transplants would be carried out under the supervision of a qualified arborists and had to follow "a set of established standards for government contracts".

This article appeared in the South China Morning Post print edition as Park's benefits extend 'beyond its borders'